alternator/regulator recommendations

[Stuart]

Cant seem to get technical support and this forum is supposed to tell me what i need to know
The engine is a 2001 mercruiser 5.7 L MPI 300 HP whole fresh water cooled. 360 hours original.
Boat is a 2002 Shamrock 246 Walk around for ocean fishing Channel Islands to San Diego and offshore
The drive belt is 13/16” 6 groove. The crankshaft pulley is 5.5” diameter and the existing pulley is 2.5”. Engine idle RPM is 600. Max RPM 5400. Cruising is at 3400 RPM. I would like to keep the alternator pulley size the same so a standard belt will work. I had considered changing the pulley size to increase RPM at slower speeds though.
The new batteries are: starter, Lifeline AGM 80 Amps and the two house batteries are Lifeline AGM 100 Amps each. All 12 volt
Will need a regulator as well and was going with Balmar, but i now understand its not compatable with Ample alternator
My average amperage load during running is about 10-20 amps, excluding the windless usage and stereo
I am looking for an alternator that provides high charge at low RPM. I will be running bait pump, squid light, deck light, anchor light, most LED. Maybe 6 amps plus fish finder all night.
I don’t have shore power, boat will be on a trailer and I need to max the charging in short periods of time and the float
I think a 120 amp alternator. See pictures of current 65 amp alternator mounting.

Looking for advice, can send jpeg pics if i new how to download of current alternator mounting with measurements

Regards,

[Coulomb]

The #4023 alternator with the NS2 12V regulator will give you about 90 Amps at 1400 RPM with your pulley ratios.

Be sure to specify the pulley you want when you order the system. Ample Power doesn't charge extra for the pulley.